The first day of the week in systems using the ISO 8601 norm and second day of the week in many religious traditions. It follows Sunday and precedes Tuesday
The first day of the week in Europe and in systems using the ISO 8601 norm and second day of the week in the USA. It follows Sunday and precedes Tuesday
Monday is the day after Sunday and before Tuesday. I went back to work on Monday The attack took place last Monday I'm usually here on Mondays and Fridays. the day between Sunday and Tuesday on Monday